cryptix.util.math

Class BigRegister

public class BigRegister extends Object implements Cloneable, Serializable

Utility class to manage a large bit-register of a given size as a mutable object.

The bits are indexed from 0 (rightmost) to size - 1, (leftmost) where size is this register's designated (at instantiation time) bit capacity.

Copyright © 1995-1997 Systemics Ltd on behalf of the Cryptix Development Team.
All rights reserved.

$Revision: 1.2 $

Author: Raif S. Naffah

Field Summary
static intMAXIMUM_SIZE
Maximum allowed number of bits in a BigRegister object.
Constructor Summary
BigRegister(int size)
Instantiate a BigRegister of a given size with all its bits set to zeroes.
Method Summary
voidand(BigRegister source)
Compute this &= source.
voidandNot(BigRegister source)
Compute this &= ~source.
voidatRandom()
Fill this BigRegister object with random data generated from the default source.
voidatRandom(SecureRandom source)
Fill this BigRegister object with random data generated from a designated source.
intbyteValue()
Return the rightmost byte value in this BigRegister.
voidclearBit(int n)
Set the bit at the designated position to 0; ie. clear it.
Objectclone()
Return a reference to a duplicate of this.
intcompareTo(BigRegister x)
Compare this BigRegister's contents to that of the argument, returning -1, 0 or 1 for less than, equal to, or greater than comparison result.
intcountSetBits()
Return the number of bits set (to 1) in this.
voidflipBit(int n)
Flip the value of the bit at the designated position.
intgetBit(int n)
Return 1 or 0 if the designated bit was set or cleared respectively.
longgetBits(int n, int count)
Return count bits starting at offset n framed in a long, right justified and left padded with binary zeroes.
intgetSize()
Return the size of this object as specified at its instantiation time.
inthighestSetBit()
Return the index of the leftmost non-zero bit in this.
intintValue()
Return the rightmost 32-bit value in this BigRegister as an int.
voidinvertOrder()
Invert the bit order of the current contents of this.
booleanisSameValue(BigRegister x)
Return true if the parameters of the BigRegister x (size and bits) are equal to this one; false otherwise.
voidload(BigRegister source)
Copy the argument's value into this.
voidload(byte[] source)
Copy the bit values from a byte array into this.
longlongValue()
Return the rightmost 64-bit value in this BigRegister as a long.
intlowestSetBit()
Return the index of the rightmost non-zero bit in this.
voidnot()
Compute this = ~this.
voidor(BigRegister source)
Compute this |= source.
voidreset()
Reset to zeroes all this BigRegister's bits.
voidrotateLeft(int n)
Circular left shift over the size of this register.
voidrotateRight(int n)
Circular right shift over the size of this register.
voidsetBit(int n)
Set the bit at the designated position to 1.
voidsetBits(int n, int count, long value)
Set count bits starting at offset n to a given value.
voidshiftLeft(int n)
Execute a left shift of this BigRegister's contents by a given number of bit positions.
voidshiftRight(int n)
Execute a right shift of this BigRegister's contents by a given number of bit positions.
booleantestBit(int n)
Return true if the designated bit is set or false otherwise.
byte[]toByteArray()
Return a copy of this BigRegister's contents in a byte array with the LSB at index position 0.
StringtoString()
Return a formatted String representation of the binary contents of this.
BigRegistervalueOf(long n)
Return a BigRegister, of the same size as this set to the specified value.
voidxor(BigRegister source)
Compute this ^= source.

Field Detail

MAXIMUM_SIZE

public static final int MAXIMUM_SIZE
Maximum allowed number of bits in a BigRegister object.

Constructor Detail

BigRegister

public BigRegister(int size)
Instantiate a BigRegister of a given size with all its bits set to zeroes.

Parameters: size Number of meaningful bits in this object.

Throws: IllegalArgumentException If the argument is less than 2 or greater than the maximum allowed value.

See Also: MAXIMUM_SIZE

Method Detail

and

public void and(BigRegister source)
Compute this &= source.

Throws: IllegalArgumentException If the argument is of different size than this.

andNot

public void andNot(BigRegister source)
Compute this &= ~source.

Throws: IllegalArgumentException If the argument is of different size than this.

atRandom

public void atRandom()
Fill this BigRegister object with random data generated from the default source.

atRandom

public void atRandom(SecureRandom source)
Fill this BigRegister object with random data generated from a designated source.

byteValue

public int byteValue()
Return the rightmost byte value in this BigRegister.

Returns: The rightmost byte value in this.

clearBit

public void clearBit(int n)
Set the bit at the designated position to 0; ie. clear it.

Parameters: n The bit position to alter.

Throws: IllegalArgumentException If the argument would cause an ArrayOutOfBOundsException while accessing the bits array.

clone

public Object clone()
Return a reference to a duplicate of this.

compareTo

public int compareTo(BigRegister x)
Compare this BigRegister's contents to that of the argument, returning -1, 0 or 1 for less than, equal to, or greater than comparison result.

Parameters: x A BigRegister object to compare to.

Returns: -1, 0, +1 If the contents of this object are respectively less than, equal to, or greater than those of the argument.

countSetBits

public int countSetBits()
Return the number of bits set (to 1) in this.

Returns: The number of set bits in this.

flipBit

public void flipBit(int n)
Flip the value of the bit at the designated position.

Parameters: n The bit position to alter.

Throws: IllegalArgumentException If the argument would cause an ArrayOutOfBOundsException while accessing the bits array.

getBit

public int getBit(int n)
Return 1 or 0 if the designated bit was set or cleared respectively.

Parameters: n The index of the bit to retrieve.

Throws: IllegalArgumentException If the argument would cause an ArrayOutOfBOundsException while accessing the bits array.

getBits

public long getBits(int n, int count)
Return count bits starting at offset n framed in a long, right justified and left padded with binary zeroes.

Parameters: n The index of the first bit to retrieve. count Number of bits to retrieve.

Returns: Right justified count bits starting from bit index n in a java long.

Throws: IllegalArgumentException If any of the arguments would cause an ArrayOutOfBOundsException while accessing the bits array, or count is < 1 or > 64.

getSize

public int getSize()
Return the size of this object as specified at its instantiation time.

Returns: The size of this object as specified at its instantiation time.

highestSetBit

public int highestSetBit()
Return the index of the leftmost non-zero bit in this.

Returns: Index of the leftmost non-zero bit in this, or -1 if all bits are zeroes.

intValue

public int intValue()
Return the rightmost 32-bit value in this BigRegister as an int.

Returns: The rightmost 32-bit value in this as an int.

invertOrder

public void invertOrder()
Invert the bit order of the current contents of this.

isSameValue

public boolean isSameValue(BigRegister x)
Return true if the parameters of the BigRegister x (size and bits) are equal to this one; false otherwise.

NOTE: the equals method is not used, because this is a mutable object (see the requirements for equals in the Java Language Spec).

Parameters: x BigRegister to test for equality.

Returns: true iff x has equal size and contents.

load

public void load(BigRegister source)
Copy the argument's value into this.

Throws: IllegalArgumentException If the argument is of different size than this.

load

public void load(byte[] source)
Copy the bit values from a byte array into this. Byte array order is assumed to have its Least Significant Byte (LSB) at index position 0. This format mirrors that of the output returned by the toByteArray() method.

Bits unprovided for in the source array are cleared. It is a more tolerant way of initialising a register than that obtained by invoking the same method with a BigRegister argument.

Parameters: source The source bits organised in a byte array with their LSB at index 0.

Throws: IllegalArgumentException If the argument is of greater size than this.

See Also: BigRegister

longValue

public long longValue()
Return the rightmost 64-bit value in this BigRegister as a long.

Returns: The rightmost 64-bit value in this as a long.

lowestSetBit

public int lowestSetBit()
Return the index of the rightmost non-zero bit in this.

Returns: Index of the rightmost non-zero bit in this, or -1 if all bits are zeroes.

not

public void not()
Compute this = ~this.

or

public void or(BigRegister source)
Compute this |= source.

Throws: IllegalArgumentException If the argument is of different size than this.

reset

public void reset()
Reset to zeroes all this BigRegister's bits.

rotateLeft

public void rotateLeft(int n)
Circular left shift over the size of this register.

Effectively compute this = this << n | this >> (size - n).

If the number of positions to rotate by is negative, then a right instead of left rotation is executed.

rotateRight

public void rotateRight(int n)
Circular right shift over the size of this register.

Effectively compute this = this >> n | this << (size - n).

If the number of positions to rotate by is negative, then a left instead of right rotation is executed.

setBit

public void setBit(int n)
Set the bit at the designated position to 1.

Parameters: n The bit position to alter.

Throws: IllegalArgumentException If the argument would cause an ArrayOutOfBOundsException while accessing the bits array.

setBits

public void setBits(int n, int count, long value)
Set count bits starting at offset n to a given value.

Parameters: n The index of the first bit to set. count Number of bits to set. value New bits value, right justified in a long.

Throws: IllegalArgumentException If any of the arguments would cause an ArrayOutOfBOundsException while accessing the bits array, or count is < 1 or > 64.

shiftLeft

public void shiftLeft(int n)
Execute a left shift of this BigRegister's contents by a given number of bit positions. If the number is negative, a right shift is executed.

Parameters: n Number of bit positions to shift by. If this value is negative then a shift in the opposite direction is executed.

shiftRight

public void shiftRight(int n)
Execute a right shift of this BigRegister's contents by a given number of bit positions. If the number is negative, a left shift is executed.

Parameters: n Number of bit positions to shift by. If this value is negative then a shift in the opposite direction is executed.

testBit

public boolean testBit(int n)
Return true if the designated bit is set or false otherwise.

Parameters: n Index of the bit to test.

Returns: true if the designated bit is set or false otherwise.

toByteArray

public byte[] toByteArray()
Return a copy of this BigRegister's contents in a byte array with the LSB at index position 0. This format is compatible with the load([B) method of this class.

Returns: The bits of this in a byte array with the LSB at index position 0.

toString

public String toString()
Return a formatted String representation of the binary contents of this.

Returns: A formatted string representation of the binary contents of this.

valueOf

public BigRegister valueOf(long n)
Return a BigRegister, of the same size as this set to the specified value.

Returns: A BigRegister, of the same size as this set to the specified value.

xor

public void xor(BigRegister source)
Compute this ^= source.

Throws: IllegalArgumentException If the argument is of different size than this.